Apparatus for supporting and conducting electric current to a load



Aug. 24, 1965 Filed April 2 1963 P. J- WOODING ELECTRIC CURRENT TO ALOAD m VA m VA VA VA %d l I I 3 Sheets-Sheet 1 INVENTOR.

FATE/CK .l. WOOD/N6 ATTORNEY Aug. 24, 1965 P. J. woooms APPARATUS FORSUPPORTING AND CONDUCTING ELECTRIC CURRENT TO A LOAD 3 Sheets-Sheet 2Filed April 2 1963 INVENTOR. PATRICK J. WOOD/N6 BY 2 g 2/ S ATTORNA'VAug. 24, 1965 P. J. WOODING APPARATUS FOR SUPPQRTING AND CONDUCTINGELECTRIC CURRENT TO A LOAD 5 Sheets-Sheet 5 Filed April 2 1965 INVENTOR.PAT/P/C/f J. WOOD/N6 620x400} SW ATTORNEY United States Patent 3,202,751APPARATUS FOR SUPPURTING AND CONDUCT- ING ELECTRIC CURRENT TO A LOADPatrick J. Wooding, Moorestown, N.J., assignor to Consarc Corporation,Rancocas, N .J., a corporation of New Jersey Filed Apr. 2, 1963, Ser.No. 270,027 Claims. (Cl. 13-31) This invention relates to improvedapparatus for supporting a load and conducting electric current to theload. More particularly, the apparatus described herein is intended tosupport and conduct current to a consumable electrode within an electricarc furnace, particularly a furnace of the type described in mycopending application Serial No. 270,026, filed on April 2, 1963, andentitled Consumable Electrode Vacuum Arc Furnace. The furnace thereindescribed is designed particularly for forming ingots of metal such astitanium, zirconium and the like or superalloys and high temperaturestainless steel.

In the consumable electrode vacuum arc melting furnace, a metalelectrode is melted by means of a high current, low voltage arc to forman ingot in an evacuated water-cooled copper crucible. For reactivemetals, the crucible can be cooled by other means, such as sodiumpotassium liquid metal. For some grades of metal, for example hightemperature stainless steel, the furnace may be flooded with an inertgas such as argon before, during or after melting the electrode. This isdone to preserve the alloy composition in cases where one or moreconstituents vaporize at pressures above the levels normally used forvacuum melting.

The direct current are is struck between the tip of the electrode andthe bottom of the crucible and is maintained during melting between theelectrode tip and the molten top surface of the ingot being formed.Normally, this melting process takes place at pressure levels between.001 and 1.0 millimeter of mercury with the vacuum system workingcontinuously to remove the evolved gases.

The electrode to be melted carries a heavy electrical current to supportthe arc, and the electrode is fed into and consumed by the arc.Commonly, the electrode is elongated and suspended by one end and feddownward. Under this method of creating heat and ultimately of meltingthe desired metal, some diflicult problems are encoun tered. Theelectrode must be physically connected within the furnace to asupporting structure and must be electrically connected to a powersupply. The electrical connection, moreover, must be sufiicientlyconductive to carry a heavy electrical current efiiciently within thehigh temperature environment.

The consumable arc furnace of the type shown in the above-mentionedpatent application utilizes electrodes of finite length. The electrodesemployed to produce heavy ingots are necessarily long and cumbersome,and difficulty has been encountered in previous furnace designs inobtain-ing correct alignment and smooth and efiicient control of thelowering action so that proper arcing and melting conditions may bemaintained in the furnace.

In order to achieve a homogeneous ingot free of pipes and axialdiscontinuities, it is necessary to maintain the arc length at a minimumWithout causing short-circuiting. Under these conditions, the length ofelectrode burn-off minus the length of ingot build-up in the crucibleequals the distance traveled by the electrode. It can readily be seenthat as the diameter of the ingot is smaller than the crucible, theelectrode will always be traveling downward. The speed of travel willdepend upon the diameter of the electrode with respect to the diameterof the crucible. For example, in one practical embodiment of the presentinvention wherein the electrode was 26 inches in diameter and thecrucible approximately 30 inches in di- 3,ZZ,75l Patented Aug. 24, 1965ice ameter, the speed of travel of the electrode at a metallurgicallyacceptable melt rate was approximately .03 inch per minute.

The information above is merely illustrative of the problem solved bythe present invention. That is, the electrode movement must be extremelyaccurately controlled during the melting operation, while still beingcapable of high speeds during set-up operations. That is, when theelectrode is initially positioned, it must be done so at reasonably fastspeeds so that little time is lost between operations.

Therefore, it is the general object of this invention to avoid andovercome the foregoing and other difliculties of the prior art practicesby the provision of a new and better apparatus for supporting andconducting electric current to a load.

A further object of this invention is to provide a new and betterapparatus for supplying electric current to a consumable arc electrodewhile accurately positioning the same.

A still further object is to provide a better and more simple consumablearc electrode support which utilizes the current carrying rod as ahydraulic piston for accurate positioning of the electrode.

Another object of this invention is the provision of a new and simplerapparatus for controlling the movement of an electrode in a consumablearc furnace which eliminates the need for complicated mechanical andelectrical apparatus on the housing.

Another object of the present invention is the provision of a new andbetter apparatus for providing electric current to a consumable arcelectrode while accurately positioning the same wherein the apparatus ismounted for rotative movement so that it can be utilized with two ormore crucibles.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there is shown in thedrawings a form which is presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIGURE 1 is a vertical sectional view of the furnace in accordance withthe present invention.

FIGURE 2 is a top plan view of the furnace in accordance with thepresent invention.

FIGURE 3 is a vertical sectional view of the head of the furnace shownin FIGURE 1.

FIGURE 4 is a sectional view 4-4 in FIGURE 1.

FIGURE 5 is a sectional view 5-5 in FIGURE 4.

FIGURE 6 is a sectional view taken along the lines 6-6 in FIGURE 1.

Referring to the drawing in detail, wherein like numerals indicate likeelements, there is shown in FIGURE 1 a consumable electrode electric arcfurnace designated generally as 8. The furnace 8 includes a head adaptedto be alternatively and sequentially used with a pair of crucible units10 and 10. The units 10 and 10 are identical. Accordingly, only the unit10 will be described in detail.

The crucible units 10 and 10 extend into a pit and are supported independing relationship from a frame 12. Frame 12 is a prefabricated unitwith cut out holes to receive the crucible units and other elements ofthe furnace 8. Frame 12 includes plates 13 and 15 supported by ledge 17in the pit. The frame 12 facilitates ease of installation since it isthe core of a prefabricated unit comprising other elements to bedescribed hereinafter. An annular water jacket flange 16 having a waterjacket 18 depending therefrom is supported by but is not secured to theframe 12. A crucible flange 20 having a taken along the lines takenalong the lines crucible 22 depending therefrom is supported by but notsecured to the flange 16. An O-ring seal is provided between the flanges16 and 20.

Water or other coolant medium is adapted to be circulated in the space24 between the crucible 22 and the water jacket 18. The crucible 22 ismade from copper and provided with a taper of approximatelythree-fourths of an inch from top to bottom to facilitate ingotstripping. The crucible 22 is provided with a copper base 34 which isspaced from and substantially parallel to the bottom plate 26 on thewater jacket 18. A housing 28 is secured to the bottom plate 26. Wateror other coolant medium is introduced through conduit 30 into thehousing 28 and through sleeve 32 into the space 35 between the base 34and plate 26. J

The lowermost end of the crucible 22 terminates in a stainless steelring 36. The base 34 is removably coupled to the ring 36 by bolts whichextend through a spider ring 38. The spider ring 38 is provided withspiders 42. Each spider arm 42 has a centrally disposed notch withinwhich is disposed a spider hub 44. The uppermost surface of the ring 38and hub 44 are notched so as to provide for maximum circulation of wateror other coolant adjacent the base 34.

An electrode 46 is adapted to be remelted within the crucible 22. Itwill be noted that the diameter of the electrode 46 is smaller than thediameter of the crucible 22 so as to provide a vacuum gap as iswell-known in the art. The electrode 46 is preferably provided with astub 48 which cooperates with a clamp 50 to suspend the electrode 4.6within the crucible 22. For the purposes of the present invention, theclamp 50 may be any one of a Wide variety of conventional clamps.Preferably the clamp 50 is of the type disclosed in copending patentapplication Serial No. 253,220 filed on January 22, 1963 and entitledElectrode Stub Clamp.

The clamp 50 is connected to a water-cooled current carrying ram 52which is supported by ahead 54. The

head 54 includes a hollow water-cooled body 56 having a coolant chamber58 in the walls thereof. The body 56 is provided with a radiallyoutwardly directed flange 60 adapted to mate with the flange 20 in thelowermost position of the body 56 as will be made clear hereinafter. Thehead 54 also includes a cylinder 62. The cylinder 62 has a base 64coupled'to the body 56 with an electrical insulation material 66disposed therebetween thereby electrically isolating the cylinder 62from the body 56. The ram 52 extends through a vacuum seal 68, throughthe cylinder 62, and extends the'reabove. In passing through thecylinder 62, the ram 52 extends through guide seals 70 and 72. I v

The ram 52 has an outer hard chrome-plated steel sleeve 77 to carry theweight of the electrode 46. A

. 7 piston 74 is fixedly secured to the outer peripheral surface 77 ofthe ram 52 in any conventional manner such as by welding. The piston 74is adapted to be reciprocated within the cylinder 62 by selectivelyintroducing a hydraulic fluid medium into the cylinder 62 by way ofconduits 76 and 78.

A current carrying copper tube 79' is disposed within the ram 52 andspaced inwardly from the chrome-plated steel sleeve 77. The uppermostend of ram 52 terminates in a head cap 80. One or more current carryingcables 82 extends through the head cap 80 and is coupled to the currentcarrying copper tube '79. Also, one or more coolant carrying conduits 84and 35 extends through the head cap 80 to introduce coolant down throughthe copper tube 79 and remove coolant which passes through suitableopenings 81 at the base of tube 79 from the space between the outerperipheral surface of the tube 79 and the inner peripheral surface ofthe sleeve 77. Watercooled current carrying electrical conduits 82 and84 are utilized to introduce both the cooling water and the current tothe ram 52 and carry the cooling water away from the ram'in a seriescircuit. The conduits 82 and. 84 are flexible hose-covered cables whichallow ram 52 to reciprocate in an upright direction withoutinterference.

Thus, the ram 52 is adapted to extend vertically upwards to become thepiston rod of a double-acting hydraulic cylinder 62 mounted directlyabove the furnace head 56. The piston 74 is arranged for friction-freemovement in the cylinder, is welded to the ram 52, or piston rod, andextends through the top 72 of the doubleacting cylinder to facilitatepower and water pickup.

Thus, it is possible to adapt a fully automatic wellproved hydraulicsystem to handle the movement of the electrode during all its modes ofoperation. The system permits the application of suflicient power toraise or lower the heaviest electrode, and is sufficiently compact sothat the natural frequency of the over-all hydraulic suspension systempermits extremely fast regulator response. Thus, it is able to regulatethe lowering of the electrode at speeds as low as .005 inch per minuteunder manual melting conditions and even less under automaticconditions.

The hydraulic system discussed above is operative during the sixdifferent modes of operation of the furnace. That is, during manualhandling, it is capable of high speeds for raising and lowering andcreep speeds for raising and lowering. Additionally, during melting, thehydraulic system may be used manually, semi-automatically, or as part ofan automatic/system. Further, if control power or a hydraulic componentfails, the operator can complete a melt using a hand pump and needlevalve in a truly manual operation.

This type of hydraulic system has a number of advantages over existingelectro-mechanical differential suspension systems. The most importantof these advantages are an improvement of at least 3/1 in response time,fewer moving parts, and simplification of the over-all furnacemaintenance requirement since one basic hydraulic system can be utilizedfor all the motions of the furnace.

The head 54 is suported for reciprocation toward and away from thecrucible unit 10 and for rotation through an arc of approximately 120,as illustrated in FIGURE 2, by means of a conduit 86 which is the mainelement through which the crucible 22 is evacuated during melting. Theconduit 86 includes a first conduit section 88 telescopically coupled toa second conduit section 90. Section $8 is provided with a radiallyoutwardly directed flange 92 adapted to cooperate with a radiallyoutwardly directed flange 94 on the upper end of conduit section whenflange 60 is mated with flange 20.

- Flange 94 is perferably provided with an O-ring seal or the like onits upper surface. Conduit section 88 is guided for reciprocation withrespect to conduit section 90 by a single centrifugally cast bearing 96shrunk into the housing 96. There is no vacuum seal between the conduitsections 83 and '90 except for the seal provided when the flanges 92 and94 are juxtaposed to and engaging one another. Hence, the telescopicarrangement between sections 88 and 90 is materially simplified sincethe necessity for having a rotary and/or sliding vacuum seal has beeneliminated.

One end of piston rod 98 is coupled to conduit section 28. The other endof piston rod 93 is coupled to a piston (not shown) disposed withincylinder 100. The lowermost end of cylinder 100 is connected to dirtbucket 102 which in turn is removably coupled to the stationary conduitsection 90 by bolts 103. Motive fluid may be con veniently introducedinto the cylinder 100 by conventional flexible conduits connectedexternally of the vacuum system to the bottom flange of cylinder 100which is also the bottom flange of bucket 102. A conduit elbow 1.04 iscoupled to conduit section 90 adjacent the lowermost end thereof tofacilitate and cause the flow of removed vapors to make a turn. Hence,elbow 104 is coupled to conduit section 106 which extends substantiallyparallel to conduit section 90.

The conduit section 106 may be provided above floor level with aselectively operable vacuum valve 108. A vacuum pump or the like 110 iscoupled to the conduit 106 to facilitate evacuation of the crucible 22during melting.

As shown more clearly in FIGURES 1 and 6, a cylindrical sleeve 105 issupported at its lower end :by the elbow 104. Sleve 105 has a diameterwhich is less than the diameter of conduit section 88. Sleeve 105 isprovided with longitudinally extending slots 107, 109 and 111 extendingdownwardly from the upper edge thereof and spaced approximately 60apart. The conduit section 88 is provided with a radially inwardlydirected projection 113 which is adapted to be disposed in one of theslots 107, 108 and 111 when the head 54 is in its lowermost position.

When the projection 113 is disposed within the slot 111, the head 54 isdisposed over the crucible 10. When the projection 113 is disposedwithin the slot 109, the head 54 is disposed over the change station112. When the projection 113 is disposed within the slot 107, the head54 is disposed over the crucible unit The slot 109 may be omitted if thehead 54 is not to be lowered at change station 112.

The upper end of the sleeve 105 is reinforced internally by a ring 115.When the head 54 is not disposed over the crucible units 10 or 10 or thechange station 112, the upper end of the sleeve 105 will be in contactwith the lower surface on the projection 113 thereby preventing descentof the head 54. This provides a precautionary feature to enable workmento work on the head 54 with confidence that the same will not descend.The lowermost end of the sleeve 105 is provided with an opening 1117providing communication between elbow 104 and the interior of sleeve105.

A motor means is provided to selectively rotate the head 54 and conduitsection 88 relative. to the crucible units when the head 54 is in itsuppermost position so that projection 113 clears the upper end of sleeve105.

Such motor means includes a motor 120 supported by the plate of theframe 12.

The motor 120 is provided with an output splined shaft 122 which extendsupwardly through a hole in plate 13 of the frame 12. The upper end ofthe shaft 122 is provided with a bearing 124 which in turn is supportedfrom the conduit 1% by a standard 126. A ball nut 128 surrounds theshaft 122 and is disposed for reciprocal movement therealong. The ballnut 128 includes a plurality of balls which partially extend into thesplines on the splined shaft 122. While the ball nut 128 may reciprocatealong shaft 122, the ball nut 128 will transmit any rotary motionimparted to the shaft 122 by the motor 120.

As shown more clearly in FIGURES 4 and 5, the ball nut 128 is providedwith a top flange 130 and a bottom flange 132 and a pinion 134 betweenthe flanges. The pinion 134 is in meshing engagement with the outerperiphery of a gear 136.

The gear 136 is fixedly secured to the flange 92 on the conduit section88. The top flange 130 is adapted to overlie the gear 136. The bottomflange 132 is adapted to be juxtaposed to the lowermost surface of thegear 136. Accordingly, the ball nut 128 will reciprocate with the gear136 and yet be capable of rotatingly driving the gear 136 when thepinion 134 is closely supported by bearing 124 at the upper end oftravel.

The frame 12, conduit sections 88, 104, 106, cylinder 100, motor 120,shaft 122, etc., may be shipped as a prefabricated unit capable of beinginserted into the pit. This feature enables the installation of afurnace to be accomplished more rapidly. Thereafter, the remainingcomponents may be provided in the orientation illustrated by means oflift hooks or the like.

A complete description of the furnace and the manner of rotation of thehead 54 is shown in my copending application Serial No. 270,026 filed onApril 2, 1963 and entitled Consumable Electrode Vacuum Arc Furnace.

The operation of the furnace 8 is as follows:

With the head 54 disposed over the change station 112, an electrode 46may be positioned within the water jacket 18, as illustrated, by meansof an overhead crane. By means of motor 120, the head 54 will be rotatedto a disposition over the electrode. By introducing a motive fluidthrough conduit 76, the ram 52 may be caused to descend to a positionwherein the clamp 50 will be coupled to the stub 48. Thereafter, motivefluid will be introduced into cylinder 62 through conduit 78 and removedthrough conduit 76 to facilitate raising of the ram and the electrode tothe phantom position illustrated in FIGURE 1. Prior to raising theelectrode, the electrode will have been centered with respect to thecrucible so that proper orientation will be attained during the melting.

Thereafter, the motive fluid in cylinder maintaining head 54 in itselevated position will be slowly removed, thereby causing the head 54 todescend to a position wherein the flanges 60 and 20 will be juxtaposedto one another and in sealing contact. At the same time, the lowermostend of the electrode will be spaced from the base 34. Valve 108 may nowbe opened and the space between the electrode and the crucible evacuatedby pump 110 by way of the body 56 and the conduit 86. When the desiredcontrolled atmosphere is attained, electrical power may be coupled tothe electrode by way of pipe 79, clamp 50 and stub 48 to strike an arebetween the lowermost end of the electrode and the base 34.

By means not shown and conventional in the art, the arc gap may besensed and the ram 52 caused to descend by introducing a motive fluidthrough conduit 76 as the electrode is consumed. Eventually, theelectrode will be consumed until only a short stub indicated by thedotted line at the upper end of the electrode in FIGURE 1 remains. Thiscondition may be detected and signaled by any convenient means. Theconsumed electrode is permitted to remain within the crucible 22 for asuflicient period of time so as to permit cooling of the ingot until themolten pool at the top end of the ingot has fully solidified. As ageneral rule, the head 54 will remain sealed to the crucible until achilled skin has formed on the surface of the molten pool. At thispoint, the power is shut off and valve 108 may be closed. Thereafter,the vacuum seal is broken and the head 54 is raised by means of cylinder100 and piston rod 98 to a point where projection 113 clears the upperend of sleeve 105. Since the head moves relative to the molten pool, themolten pool will not be disturbed and the chilled skin will protect thepool from contamination. If the molten pool is disturbed before it issolidified, a substantial portion of the ingot may be wasted.

The head 54 is then rotated to a position so that the stub is above thechange station 112. At the change station 112, the stub 48 is separatedfrom the clamp 50. While the head 54 was supporting the electrode beingmelted in unit 10, a crane will have previously provided a new electrodeand crucible in unit 10'. Hence, the head 54 may be rotated to aposition over the new electrode in unit 10 and the above operationrepeated. As soon as the previously formed ingot has solidified, it maybe removed by a crane and a new crucible and electrode substitutedtherefor.

If it is desired that the controlled atmosphere within the crucibleduring melting be inert gas rather than vacuum, the inert gas may beintroduced through conduit 86. Hence, the inert gas or other gas may beintroduced into the furnace body by Way of conduit 86 and removedtherefrom by means of an exhaust valve on the body 56. To facilitaterapid equalization of pressure prior to raising the head 54, the body 56may be provided with a manually operable exhaust valve 114. If desired,auxiliary tangential coolant inlets may be provided in water jacket 18to increase the coolant velocity at the outer surface of the coppercrucible 22. If desired, the support provided by ring 38, spider 42 andhub 44 may be eliminated if the base 34 is dish-shaped.

In order to provide for ease of maintenance, the pit is of sufiicientdepth so as to enable the cylinder 1% to be maintained. In order toaccomplish this, the bolts 103 will be removed. With the head 54 in itslowermost position, motive fluid will be supplied to the cylinder 1% inan attempt to raise the head. Since the lowermost end of the cylinder isno longer coupled to the elbow lltld, the cylinder 180 and receptacle102 will descend. Thereafter, any dirt or contaminant in receptacle 192may be removed and the necessary maintenance operation is performed.

The frame 12 will be provided with the necessary lifting eyes or thelike to facilitate manipulation by a crane. Also, a convenient'entry waywill be provided to facilitate the entry of a person into the pit formain- I tenance purposes and the like. Suitable bracing is providedbetween the plates 13 and 15 of the frame 12 to provide a box girderwith sufficient strength to withstand dead-load forces. For addedstrength and support, it will be noted that the bearing 96 lies in theplanes of the plates 13 and 15 of the frame 12.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specification as indicating the scope of theinvention.

I claim:

i. In an electric arc melting furnace comprising a head having anelectrically conductive water-cooled ram, said head including a mainbody having an open bottom portion adapted to cooperate with a crucibleto' define a chamber within which an electrode may be melted undercontrolled atmosphere conditions, atmosphere controlling means incommunication with said chamber for controlling the atmosphere in saidchamber, support means for moving and controlling the placement of saidhead with respect to said crucible, said head having a cylinder mountedon said main body, said electrically conductive water-cooled ram passingthrough said cylinder, said ram having a piston integral therewith insaid cylinder, hydraulic means for controlling the movement of saidpiston to raise and lower said ram, electrical supply means and watercoolant supply means connected to said ram at a point outside of saidcylinder and immediately above said cylinder, said ram extending throughsaid'cylinder into said body, and an electrode clamp mounted on said ramin said chamber and in electrically conducting relation with said ram.

2. The furnace of claim 1 wherein said support means is adapted to raiseand lower said head and additionally is mounted for rotative movement.

3. The furnace of claim 1 wherein said electrically conductivewater-cooled ram includes a first cylinder adapted to carry the weightof an electrode, said ram additionally including a second copper tuberunning the length of said ram and having its surface spaced from thesurface of said first cylinder, said water supply means being adapted tosupply water within said first cylinder and said copper tube to coolsaid copper tube, said electrical supply means being adapted to supplyelectrical current to said coppe tube I 4. The furnace of claim 3wherein said first cylinder is axially aligned with said copper tube andhas a greater inner and outer diameter than said copper tube, saidpiston being welded to the outer surface of said first cylinder, saidhydraulic fluid means being adapted to supply fluid to the top andbottom of :said cylinder to control the movement of said piston in saidcylinder and thereby control the movement of said ram.

5. The apparatus of claim 6 wherein said electrical supply meansincludes a flexible conduit having an electrical conductor therethroughand said coolant fluid supply means includes a fluid conduit about saidelectrical conductor to form said flexible conduit.

6. Apparatus for supporting and conducting electric current to a loadcomprising a cylinder having first and second ends, a ram extendingthrough said first and second ends, said ram having a first endextending through said first cylinder end and being adapted to beconnected to a load, said ram having a second end passing through saidcylinder second end and being adapted to be connected to a source ofelectric current, said ram being electrically conducting along thelength thereof, said ram having a hollow portion, said ram second endbeing adapted to be connected to a source of coolant fluid to besupplied to said ram hollow portion to cool said ram, a piston integralwith the surface of said ram in said cylinder, and hydraulic meansconnected to said cylinder for controlling the movement of said pistonand thereby controlling the movement of said ram, said ram including acopper tube extending from said ram first end to said ram second end toconduct electrical current therebetween, said ram additionally includinga steel sleeve axially in line with said copper tube and having agreater inner diameter than the outer diameter of said copper tube toform a channel between the outer surface of said copper tube and theinner surface of said steel sleeve, said steel sleeve extending betweensaid ram first end and said ram second end, said steel sleeve beingadapted to support a load connected to said first end, said coolantsupply means being adapted to supply coolant fluid within said coppertube and within the chamber between said copper tube outer surface andsaid steel sleeve inner surface.

7 The furnace of claim 2 wherein said support means is adapted to rotatesaid head about an axis parallel to and spaced from the axis of saidwater-cooled ram.

8. Apparatus comprising a head having an open bot tom, a cylindersupported by the head, a hollow ram in said cylinder with a first end ofthe ram extending out of one end of the cylinder and the second end ofthe ram extending out of the other end of the cylinder, seal meansbetween said ram and the ends of the cylinder, a piston in said cylinderand connected to said ram, hydraulic conduit means associated with saidcylinder for moving said ram, electrode support means mounted on saidsecond end of the ram, an electrical conductor in said ram andelectrically coupled to said support means, and a vacuum seal betweensaid head and a portion of said ram between the piston and said secondend of the ram.

9. Apparatus in accordance with claim '8 wherein an electrical conductoris hollow, conduit means for introducing coolant through said ram firstend into said hollow conductor.

, 10. Apparatus in accordance with claim 8 including means electricallyisolating said ram and cylinder from said head.

RICHARD M. woon, Primary Examiner.

8. APPARATUS COMPRISING A HEAD HAVING AN OPEN BOTTOM, A CYLINDRICALSUPPORTED BY THE HEAD, A HOLLOW RAM IN SAID CYLINDER WITH A FIRST END OFTHE RAM EXTENDING OUT OF ONE END OF THE CYLINDER AND THE SECOND END OFTHE RAM EXTENDING OUT OF THE OTHER END OF THE CYLINDER, SEAL MEANSBETWEEN SAID RAM AND THE ENDS OF THE CYLINDER, A PISTON IN SAID CYLINDERAND CONNECTED TO SAID RAM, HYDRAULIC CONDUIT MEANS ASSOCIATED WITH SAIDCYLINDER FOR MOVING SAID RAM, ELECTRODE SUPPORT MEANS MOUNTED ON SAIDSECOND END OF THE RAM, AN ELECTRICAL CONDUCTOR IN SAID RAM ANDELECTRICALLY COUPLED TO SAID SUPPORT MEANS, AND A VACUUM SEAL BETWEENSAID HEAD AND A PORTION OF SAID RAM BETWEEN THE PISTON AND SAID SECONDEND OF THE RAM.